A comparative study of iron concentrates by Mössbauer spectroscopy and optical microscopy.

Abstract

Five samples of iron-ore concentrates used for the production of pellets were heated at different temperatures under air atmosphere and characterised by chemical analysis, optical microscopy and Mössbauer spectroscopy. In all samples it was observed the presence of specular hematite, martite, and goethite in different proportions, whereas one sample also contains 15% (w/w) of magnetite. The presence of residual goethite was observed in the samples heated at 300◦C, whereas the magnetite was only converted to hematite after heating at 900◦C. However, the results of the optical microscopy pointed to the existence of large amounts of goethite even in the samples heated at 900◦C, which is obviously incorrect. Therefore, it can be concluded that the reflectance of hematite derived from goethite is similar to that of the original goethite, limiting the use of optical microscopy for these types of samples.